1. Field of the Invention
The present invention relates to a line for continuously annealing and pickling a stainless steel strip.
2. Description of the Related Arts
In recent years, the following method is carried out by a line for continuously annealing and pickling a stainless steel strip, a stainless steel strip (S) is annealed by a catenary type continuous annealing furnace (not shown); the stainless steel strip (S) is cooled by a spray type water cooling zone 1; the stainless steel strip (S) is dewatered by dewatering means 5 comprising a wiper roll unit 3 and an air nozzle unit 4 unit provided in the exit 2 of the water cooling zone 1; and then, the stainless steel strip (S) is electrolyzed in a tank 6 containing a neutral salt electrolytic solution to remove a scale formed on the surface of the stainless steel strip (S) while it is annealed.
In the neutral salt electrolytic processing, it is known as disclosed in Japanese Patent Laid-Open Publication No. 62-124232 that pickling effect is favorable with the rise of the temperature of the neutral salt electrolytic solution (W) even though current density is small.
When the temperature of the neutral salt electrolytic solution (W) is set to 60.degree. to 100.degree. C., the temperature of the stainless steel strip (S) is set to 60.degree. to 100.degree. C. at the exit of the water cooling zone 1 in the conventional equipment. As a result, the temperature of the stainless steel strip (S) in the longitudinal direction thereof is different (maximum: 50.degree. C.) from that in the widthwise direction thereof. Thus, the stainless steel strip (S) has a low temperature region.
Accordingly, with the fall of the temperature of the neutral salt electrolytic solution (W), pickling effect degrades. Consequently, current density becomes high, i.e., power consumption becomes great. In addition, the stainless steel strip (S) has high and low temperature regions. As a result, the temperature of the neutral salt electrolytic solution which is in contact therewith is not uniform. As such, a uniform scale removal cannot be accomplished.
The dewatering means 5 is incapable of dewatering the stainless steel strip (S) from the surface thereof completely and the stainless steel strip (S) slips on a bridle roll 7. As a result, an abnormal wear occurs on the surface of the bridle roll 7 and the tension of the stainless steel strip (S) fluctuates, thus resulting in various troubles.